Benzocaine-Induced Methemoglobinemia

Pradeep M. Gupta, MD, Deepa S. Lala, MD, Edward L. Arsura, MD, Department of Internal Medicine, University of Virginia School of Medicine, and VA Medical Center, Salem, Va.

South Med J. 2000;93(1) 

In This Article


Benzocaine spray is widely used for topical anesthesia in a variety of procedures, including endotracheal intubation, bronchoscopy, laryngoscopy, upper endoscopy, TEE, induction of anesthesia, nasogastric tube placement, and minor surgery. Benzocaine-induced methemoglobinemia, though rare, can be fatal, and physicians using this agent should be aware of this side effect. The diagnosis is mainly clinical, with a chocolate-color cyanosis unresponsive to oxygen therapy. A discrepancy between O2 saturation and PaO2 should alert the physician, and diagnosis should be confirmed by cooximetry. Treatment of choice is intravenous methylene blue. Methylene blue should be readily available in areas where topical anesthetics are frequently used, such as intensive care units, endoscopy units, and anesthesia induction units. Emphasis should be placed on preventive measures, prompt diagnosis, and treatment.


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